Windows 7: Is unable to change permission changes on files.

Hello,

I've been trying to download the Texas Holdem Poker 3D edition for my Windows 7,Ultimate x64.
I acknowledged the fact that the 3D edition isn't supported by Windows 7 x64, but have derived yet another medium of achieving my means. With a little bit of help from Google, I've downloaded a Winzip THP 3D game for vista. I extracted the file. The read-me of the file instructs me to:
Enter the windows regedit and several successions of instructions starting from the path HKEY_LOCAL_MACHINE that brings me to the Title finally.
I right-click and 'Permissions for Titles' opens up.
I see 4 topics under the Group or usernames :
Systems
Administrators
Users
Trusted Installer

So as the read-me advices me to select the Administrators, I do the needful.
Then opens up another tab called Permissions for Administrators where I see three options and two check-boxes on the right side.
Full control
Read
Spcl. permissions

I tick the 'Allow' check-box for the Full control option.

When I click on Apply changes, the error message is displayed:

Unable to change permission changes on titles
Access Denied
Please help!


EDIT:
Oh please reply.
I guess my question's too complex.

Basically I wanted to change the 'title permissions' for the admin so that I could effectively use the poker application.

Only "TrustedInstaller" can modify those registry keys.